Method of treating petroleum oils



oct. 23, 1934.

W. N'. DAVIS ETAAL METHOD OF TREATING PETROLEUM OILS 3 Sheets-Sheet l Filed March 16, 1931 man: um,

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W. N. DAVIS ET AL METHOD OF TREATING. PETROLEUM OILS- 5 Sheets-Sheet 2 E'iled March 16, 1931 Oct. 23, 1934.

W. N. DAVIS ET AL METHOD OF TREIATINGy PETROLEUMJ/OILS Filed March 1G, 1931 5 Sheets-Sheet 3 UBAAJM.

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Patented Oct. 23, 1934 1,977,717

METHOD or 'rnEA'rlNc PETROLEUM olLs William N. Davis, Oakland, and William H.

Hampton, Berkeley, Calif., assignors to Standard Oil Company of California, San Francisco, Calif., a corporation of Delaware Application March 16, 1931, Serial No. 522,988

Claims. (Cl. 196-40) 'I'his invention relates to improvements in the process of removing sulfur bodies from naphtha, motor fuels and similar petroleum oils and has particular value in the treatment of cracked petroleum naphthas high in sulfur content and containing a relatively high percentage of unsaturated hydrocarbons. More particularly, this invention relates to a process of the type described in which the desulfurization is accomplished with a materially smaller amount of an acid reagent than has been used heretofore.

'I'his invention is a continuation in part of a copending application, Serial Number 236,689, filed November 30th, 1927 in the names of William N. Davis and William H. Hampton and issued on August2, 1932, as Patent No. 1,869,- 885. A

1n United States Patent Number 1,705,809 issued March 19th, 1929, to William N. Davis, et al. and in Patent No. 1,869,885, mentioned hereinabove, it is set forth that when motor fuels containing sulfur and unsaturated hydrocarbons are treated in the conventional manner with sulfuric acid for the removal of sulfur, there results a considerable loss of valuable non-sulfur bearing unsaturated hydrocarbons.. Such loss is caused by the polymerization or solution of these non-sulfur bearing unsaturated hydrocarbons by the acid at the temperatures ofthe acid treatment, which, because of the heat of reaction, may be as high as 140 F. In said patent and application it is taught that the desulfurization can be effected Without substantial polymerization or dissolving of the non-sulfur bearing hydrocarbons if the temperature of the treatment is kept down, by refrigeration, to a temperature below which the acid does not materially polymerize or dissolve the non-sulfur bearing hydrocarbons, but at which temperature the acid still extracts the sulfur bodies. The temperature which is best suited to any particular treatment depends upon such variables as the character of the oil. being treated, the nature of the unsaturated hydrocarbons, the strength of the acid used and the amount ofthe acid used.

To illustrate the advantages of the process, it is shown that when a typical cracked naphtha containing 0.75% of sulfur is treated by the prior methods with 66 Be. acid to produce a motor fuel containing only 0.15% of sulfur, there is required 1.25 pounds o acid per. gallon of naphtha, and the polymerization loss ofvaluable motor gasoline is 21%. When the same cracked naphtha is treated for the same sulfur reduction at a reduced temperature o f about 0 discovery that if the acid is applied to the naphtha by a step counterow process, the amount of acid required to effect a given sulfur reductionl is reduced about 50%. over the amount required for the same sulfur reduction by the prior method of cold treating, or the invention may be stated in another way, namely, the step counterow process results in a greater sulfur reduction for a given amount of acid. In such step counterflow process, the oil is rapidly subjected to separate applications of an acid rening agent of progressively stronger character, the oiland acid agent being entirely mixed after each application.

'I'he mixture of oil and acid is preferably cooled after each of such applications and before a succeeding application of acid agent the partially spent agent and sludge formed by the preceding application is removed.

A true counterow process is one in which the naphtha and acid 110W in opposite directions while in contact with each other, the most treated naphtha being treated with thestrongest acid. A step counterow process is one in which the naphtha is treated in a series of separate steps, the naphtha being treated progressively with stronger acids. Contrary to expectations, we rind that a true counterow process does not eiect as great a reduction in acid requirements as a step counterflow process. Furthermore, 4We find that4 the sulfur reduction is not as great with a true counterow process as the sulfur reduction which can be obtained by a step counterow process. The reason appears to be that the contact between the acid and the naphtha in the conventional counterow methodis not as good as that obtainable in a step counteriow method where each addition of acid is accompanied by thorough mechanical agitation. Furthermore, inthe preferred step counterliow method of this invention the reaction products @f .er each addition of acid reagent are removed from the oil before such oil is contacted with a succeeding batch of acid reagent, and in this manner the dilution of the acid reagent by the reaction products of a preceding application of acid is obviated.

While a stepl counterflow process accomplishes further desulfurization with each successive step, we find that the usefulness of each suc-,- cessive step decreases so rapidly that it is hardly worth while, considering the cost of each step, to employ more than about four steps.

An object of this invention is to disclose and provide a process of treating petroleum oils whereby a material reduction in sulfur content may be obtained by the use of a much smaller quantity of acid than has heretofore been thought possible.

Another object is to disclose and provide a method of treating petroleum naphthas whereby desulfurization without elimination of non-sulfur bearing hydrocarbons may be accomplished with a materially smaller amount of acid than has been used heretofore.

A still further object is to disclose and provide a step counterflow method of treating petroleum naphthas for the removal of sulfur bodies therefrom without the elimination of non-sulfur bearing unsaturated hydrocarbons.

The process will become more fullyapparent to those skilled in the art from the following description of preferred `methods of operation, reference being had to the appended drawings, diagrammatically illustrating arrangements of apparatus by means of which nthe invention may be carried into effect.

In the drawings:

Figure 1 is a diagrammatic illustration of a preferred embodiment of a four sep counterilow process.

Figure 2 is a diagrammatic illustration three step counterflow process.

Figure 3 is a diagrammatic illustration of a two step counterow process.

As shown in Figure 1 the untreated naphtha which may be a cracked naphtha from a storage tank 1 may be pumped by means of a pump 2 through one or more settlers such as the settlers 3 and 4 wherein any water in the naphtha is settled out and drawn off from the bottom loi.' the settlers. It is important that water or moisture present in the naphtha be removed before the naphtha is refrigerated as otherwise the water may freeze and clog the pipe.

If desired, the naphtha may be dried by means of a like treatment with acid or sludge containing acid, such acid or sludge being introduced into the upper portion of settlers 3 and 4 as by means of spray nozzles 5 and 6. Whenfasludge is employed such sludge may be drawn off from the bottom of the. settlers. 'The water-free naphtha may then be passed by means of a line 7 through one or more coolers orvrefrigerators 8 and 9 wherein4 the temperature of the naphtha is reduced to a point such that it will not rise above 15 or 20 F. in subsequent mixing ofa with acid or sludge. Relatively weak acid may then be introduced into the cooled naphtha by means ofthe pipe 10.

As shown in the illustrated example, instead of the acid an 'acid sludge is introduced into the cooled naphtha by means of the line 10. The mixture of naphtha and sludge may then be passed through a suitable mixing pump 11 which may be of the centrifugal type adapted to serve both as a mixer and as a booster pump. The

temperature of the mixture of naphtha and sludge or acid starts to rise immediately after mixing, due to the exothermic reaction of acid with unsaturates. The temperature of the mixture is held down to below about 20 F. by means of passing the mixture through one or more coolers or refrigeratingl means 12 and 13. The size of the cooler is so designed that the temperature rise isj usually not more than 10 or 15 F., the temperature of the mixture leaving the cooler 13 being about 10 F. so that it will not Warm up during the subsequent settling period to a temperature higher than about 20 F. The cooled mixture may then pass into a suitable settling tank such as a vertical settling ,y tank 14 wherein the sludge is allowed to settle.

The substantially sludge-free naphtha `(which ordinarily becomes warmed up to 15 or 20 F. in the settler 14) is then passed from the settler 14 through one or more coolers 15 and 16 where the temperature is again reduced to about minus 10 F. Sludge or acid is again applied to the naptha through a conduit 17. The acid or acid sludge applied through the conduit 17 is preferably stronger than that applied to the naphtha through the line 10. The strength of the acid is regulated as will become apparent from the following description by employing sludge from successive treatments of naphtha with progressively stronger acids.

The mixture of naphtha, and sludge is then passed through a centrifugal mixer and booster pump 18 where the temperature of the mixture again starts to rise, reaching about 15 or 20 F. before it is again reduced to about 10 F. in the coolers 19 and 20. The cooled mixture of naphtha and sludge is then passed to another settling tank or equivalent device such as, for example, the vertical settling tank 21 wherein the sludge settles to the bottom and is withdrawn through the line 10 which leads to the main naphtha line between the coolers 8 and 9 and the mixer pump 11.

The naphtha (from which the major portion of the sludge has been separated) then passes from the settler 21 by means of a line 22 into the coolers 23 and 24 where the temperature of the naphtha is again reduced to about minus 10 F. or to some point suflcient to prevent the naphtha from rising above 15 or 20 F. in the The subsequent mixing with acid or sludge. cooled naphtha from the cooler 24 is then contacted with a stronger acid or sludge from a pipe 25. The mixture of acid and o il is then passed through the mixer and booster pump 26 all) LIEU where the temperature rises about 10 or 15 before it is reduced to about- 10 F. in one or more coolers 27iand 28. The cooled mixture is again passed into a suitable form of settling device such as a tank 29, the sludge being withdrawn from the tank 29 through line 17, such 'A sludge being passed into the naphtha before it enters the second mixing pump 18.

'I'he naphtha from the settling tank 29 is passed through one or more coolers 30 and 31 f where the temperature is again reduced to a Amay be as low as minus 10 F. for large quantities of acid such as 0.75 lbs. per gallon of naphltha.. The cooled naphtha may then be contacted with fresh acid from a tank 32 through a valve line 33.

The naphtha and acid are thoroughly agitated in the mixer and booster pump 34 and then sent through the coolers 35 and 36 where the temperature of the oil and acid mixture is maintained and reduced to about 10' F. The refrigerated acid and treated oil then pass into the sludge settler 37 wherein the' sludge is separated from the oil and is sent back by line4 25- for addition to the naphtha at a point between the coolers 24 and 23 and the mixer pump 26.

The naphtha (substantially'free of the major portion of the-sludge) may then be sent by line 38 to any suitable apparatus lfor more completely removing sludge from the oil. For purposes of illustration the naphtha may `besent by line 38 to a separator merely consisting of a drum or tank filled with rocks or gravel or other materialhaving a large contact surface. The sludge coagulates on such packing material and settles to the bottom of the coagulator 39 from whence such sludge may be withdrawn through thetline 40.

The sludge from the separator 39 may contain some entrained naphtha which may be recovered by passing the sludge through a heater 41 and then into a settler 42 where the mixture quickly separates into an upper oily layer and a lower sludge layer. The oil thus separated from the sludge may be discharged by line'43 and mixed with the untreated naphtha. before-it enters the rst oil and acid mixer 1l. The sludge from the settler 42 may be passed as by line 44 into a storage tank 45 from which it may be sent to a recovery plant for reclaiming acid from the sludge.

If desired, the sludge treating system comprising the heater 41 and settler 42 may operate not only upon the sludge from the separator 39 but in addition it may be caused to operate upon the sludge resulting from the first acid contact that the oil was subjected to. In other words, sludge from the sludge settler 1'4 may bedischarged by line 46 into the pass into the settler 42.l

The substantially sludge-free naptha from the separator 39 may b e discharged by line 47 into one or more water treaters 48l and 49 whereinthe naphtha may be sprayed with water (either fresh' or salt) from spray nozzles. 50 supplied with `water from a line 51.l When two treaters 48 and 49 lare used, the oil may pass through them successively. After being washed, the naphtha may be discharged through a line 52 and neutralized by being subjected to the action of an alkali such as caustic, supplied from a caustic storage tank 53 by a line 54 connectedI with the naphtha line 52.

The mixture of caustic and' naphtha may then be sent to a mixer pump 55 from whence the mixture may be passed through a baille type of mixer 56.4 The mixture of caustic and naphtha may then be sent to a settler 57 from whence the spent caustic may be withdrawn either continucusly or periodically by means of a valve outlet 58. -The neutralized naphtha may be discharged by a line 59 and sent to a suitable storage tank 60 as by means of a pump 61.

In Figure 1 a process has been shown in which heater 41 and then All of the successive applications or contacts with the acid reagent may be made with progressively stronger acids without the use ofk Likewise, all of the treatments may be sludge. made lwith progressively stronger solutions without the use of fresh acid, or the treatment maybe made with .any combination of acids or solutions so long as the most treatednaphtha is treated with progressively stronger acidl re' agents.4

The process illustrated in Figure 1 is what we have termed a four step process since the y/naphtha is contacted four times with acid solution or acid. It is to be understood however,

that the process may be performed by employing from two to six or even eight steps, although, it is uneconomical tovemploy more than about four or six steps.

We find that the useful desulfurization accomplished by each additional step decreases very rapidly while the dost of each successive step increases by a constant amount.

For the treatment of a naphtha having a sulfur content of 0.20% or more, or a gasoline having a sulfur contentpf 0.15% or less, weI have found that under the present conditionsof cost of acid and equipment versus the value of naphtha treated, that it is not, always commercially practicable to go beyond four steps in the process.

In order to illustrate the decreasing value of the successive steps inv the treatment, we give three methods is greater for two step counter-- ilowthan for con-iiow treating, but decreases slightly as the number of steps is increased from two to four. This is another reason why we do not ilnd it commercially practicable to employ more than fourA treating steps. y

Figure 2 shows athree step counteriiow treating process such as is described but not' claimed in` application, Serial No.` 236,689.- Untreated naphtha from a vtank 63 passes through a cooler or` heat exchanger 64, then through a refrigerator' 65, thence to a mixing T 66 where it is contacted with relatively weak sludge from settier 67. The mixture of naphthal and sludge is passed through a mixing and boosting pump 68 and thence into a refrigerated settler 69 containing a cooling coil 70. A portion of the sludge from the bottom of the settler 69 may be recirculated through the mixing T 66 and the remainder passed to a storage tank 71.

Naphtha from settler 69 passes through a pipe tively strong sludge from a settler 74' The mixture of naphtha and sludge is passed through a mixing and boosting pump 75 and '12 to a mixing T 73 where it is mixed with relathence to settler 67 which is refrigerated byl means of a cooling coil 76. A portion of the lsludge from settler 67 is recirculated through the mixing pump '15 and the remainder is passed to mixing T 66.

Naphtha from settler 67 passes through a pipe 77 to a mixer 78 where it is mixed with fresh acid from a pipe 79 supplied from a tank 80 by a pump 81. cooler 82 in heat exchange relation to the coldV sludge from settler 69. The mixture of acid and naphtha pass from themixer 78 into a settler 74 which is refrigerated by means of a cooling coil 83. The sludge from settler '74 passes to the mixing pump '75. The temperature in the three settlers 67, '69 and 74 is maintained below 20 F. by the coils 76, 'land 83 respectively.

The treated naphtha from settler 74 passes through a pipe 84 to a storage tank 85. The cold naphtha in pipe 84 is passed through the cooler 64 in heat exchange relation with untreated naphtha from tank 63.

Figure 3 illustrates a two step counterflow process, the simplest form of step counterflow treatment. Untreated naphtha from a storage tank 86 is passed by means of a pump 87 through a water settler 88 and thence through one or more coolers, 89 and 90, where the temperature is reduced in any suitable manner to an extent sufficient to prevent the naphtha from rising above 15 or 20 F. in subsequent mixing with acid sludge; when using 0.20 lbs. of 98% acid per gallon of naphtha, this temperature is around 8 or 10 F.

The cold naphtha is contacted with sludge from a settler 91, and the naphtha and-sludge are passed through a mixing and boosting pump 92, thence through one or more coolers, 93 and 94, and into the settler 91. The sludge from the settler L91 is passed back into the untreated naphtha just before it enters the mixer 92.

The naphtha from settler 91 passes through one or morev coolers 95 and 96, to reduce the temperature of the naphtha to such a point that it shall not exceed15 or 20 F. during `subsequent contacting with acid. When using 0.20 lbs. of 98% acid per gallon of naphtha, this temperature is around .12 or 14 F. For larger amounts of acid, it should be lower and conversely, for smaller amounts of acid itv could be` higher. Acid from 'a tank 97 is contacted with the cold naphtha. 'I'he mixture is passed through a mixing and boosting pump 98 and thence through one or more coolers 99 and 100, where the temperature of -the mixture is reduced to about 10 F. The mixture passes into a settler 101 from which the sludge and naphtha are drawn off to their respective storage tanks 102 and 103.

It is to` be understood that the naphtha may be given any desired treatment preliminary to or subsequent to the process particularly describedA without departing from the substance of thev present invention which relates to the use of a step counterflow acid treatment for cracked naphthas under such conditions of refrigeration that the temperature rise which Vwould otherwise A result from .the action of sulfuric acid on unsaturates is restrained so that the temperature of. the mass is maintained below that at which` the acid causes any material amount of polymer-fi ization rof the unsaturated, non-sulfur bearing hydrocarbons.

The acid used in the treatment may be of any-v desired strength and quantity. The most suitable proportions between strength and quantity of acid can'be readily determined by experiment for any given oil and any given sulfur reductions We have employed 66 B. sulfuric acid as wellr` as weaker acids and stronger acids. 98% H2504 acidgives good results as does 1,5% fuming acid..

The acid is passed through a :,When stronger acids are used, smaller amounts are required.

'I'he temperatures employed in the process are variable. The selection of the. proper temperarture for a given naphtha ,depends upon the therefore, depends upon the amount and strength of the acid used for desulfurizing. Strong acids generate more heat than weak acids and therefore require lower treating temperatures and more eicient cooling in order to minimize polymerization of the unsaturated hydrocarbons.

Likewise, large amounts of acid generate more heat than small amounts and therefore require lower treating' temperatures. Where a vlarge percentage of sulfur must be removed from the naphtha, it is necessary to employ considerable amounts of acid.

At ordinary atmospheric temperatures, sulfuric acid polymerizes sulfur bodies to higher boiling bodies which can be subsequently separated from the naphtha by distillation.

Unfortunately, the acid likewise polymerizes a part of the valuable non-sulfur bearing hydrocarbcns suitable for motor fuel, converting them to higher boiling point hydrocarbons having lboil- ,ing points above the end boiling point of gasoline motor fuel. The loss of motor fuel through polymerization may be as much as 30%, or even 50%. 'I'he acid which spends itself in polymerizing non-sulfur bearing unsaturated hydrocarbons, is, of course, not available for desulfurization. Therefore an excess 'of acid is required in order to effect a given desulfurization of unsaturated motorvfuel if the treatment is performed without refrigeration.

As the temperature of the acid treatment is reduced, the polymerization of unsaturated nonsulfur bearing hydrocarbons is reduced, and

therefore the weakening of the acid is prevented. The acid is free to actually extract the sulfur bodies as such, and therefore at reduced temperatures less acid is required in' order to effect a given desulfurization of unsaturated motor fuel.

At reduced temperatures, the acid not only polymerizes a part of the sulfur bodies, but also dissolves a part of them. When the acid has been separated from the naphtha; it will be found that the sulfur content ofy the naphtha has been reduced materially, even before distillation, which is not true of naphthas treated at normal temperatures. Upon distillation of the naphtha, the sulfur content is still further reduced by removal of the polymerized sulfur bodies.

By treating the naphtha in a step counterow process with thorough mixing of the naphtha and sludge or acid following each contacting step, the amount of acid required in order to effect a given desulfurization is greatly decreased, as has been set forth above.

The advantages of the step counterow cold- Ytreating process increase as the temperature of amount of desulfurization toI be effected, and,

treatment is decreased.' The optimum temperafrigeration and value of naphtha or gasoline,

etc. are givenf'due consideration.

The above detailed description clearly sets forth the invention. Those skilled in the art will recognize that numerous changes may be made in the steps and conditions of treatment without departing from the process taught here. All such changes as come within the scope of the appended claims are embraced thereby.

It is understood that the embodiment of the invention described herein is only one of the many embodiments this invention may take, and we do not wish to be limited in the practice of the invention, nor in the claims, to the particular embodiment set forth.

We claim: Y

1. A process of treating motor fuels containing sulfur bearing bodies and non-sulfur bearing unsaturated hydrocarbons, inwhich a part of the sulfur bearing bodies are polymerized or dissolved while excessive polymerization of the unsaturated hydrocarbons is prevented, said process comprising subjecting the motor fuel to successive separate applications of an acid refining agent of progressively stronger character, cooling the mixture of oil and acid agent after each of such applications, agitating the mixture of oil and acid agent after each of such applications, and separating and removing the sludge from the oil after each of said successive applications, the mixture of oil and acid being cooled after each of such applications to a maximum temperaturesulciently low to permit party of the sulfur bodies to be selectively removed by said acid agent and a part thereof to be polymerized andbelow the temperature at which the 'non-sulfur bearing unsaturated hydrocarbons readily polymerize.

2. A process of treating motor fuels containing sulfur bearing bodies and non-sulfur bearing unsaturated hydrocarbons, which comprises removingmoisture from the motor fuel and then polymerizing a part of said sulfur bearing bodies while preventing excessive polymerization of the unsaturated hydrocarbons by subjecting the motor fuel being treated to successive separate applications of a sulfuric acid refining agent of progressively stronger strengths in quantity suiiicient to selectively remove a part of the sulfur bodies and to polymerize a further part of said bodies at low temperatures and to effect a material rise in temperature of reaction unless restrained, agitating the mixture of motor fuel and acid agent after each of such applications, separating the resulting sludge from the motor fuel after each of such applications, and cooling the mixture of motor fuel and sulfuric acid agent after each of 'such applications, to absorb the heat of reaction and to perform the acid treatment at a maximum temperature suciently low to perremoved by said acid, and a part thereof to be polymerized and below the temperature at which the non-sulfur bearing unsaturated hydrocarbons` readily pclymerize, then finally separating the motor fuel from the acid agent and distilling the motor fuel from the polymerized bodies.

3. A sulfur removing process of treating motor fuels containing substantially no water and containing sulfur bearing bodies and nonsulfur bearing unsaturated hydrocarbons, in which a part of the sulfur bearing bodies are polymerized or dissolved While excessive poly-A merization of-the unsaturated. hydrocarbons is prevented, which comprises contacting such motor fuel with sulfuric acid of such strength and quantity as to have the capacity at low temperatures of selectively removing a part of the sulfur bodies and to polymerize a further part of said bodies and to effectl a material risel from a later acid treating step to the motor fuel at a point prior to said later acid treating step, applying fresh acid as a last step in the process, and applying the progressively stronger sludges to the progressively more treated motor fuel; the acid treatments being performed, by absorbing heat of reaction, at a maximum temperature sufficiently low to permit a part of the sulfur bodies to be selectively removed by said acid, and a part thereof to be polymerized, and below the temperature at which the non-sulfur bearing unsaturated hydrocarbons readily polymerize, separating the motor fuel from the acid Vand acid reaction products, and distilling the motor fuel from the polymerized bodies.

4. In a process of treating motor fuels containing sulfur bearing bodies and non-'sulfur bearing unsaturated hydrocarbons, the steps of removing a part of the sulfur bearing bodies by selective solvent action of sulfuric acid, and a part of the sulfur bearing bodies by polymerization while preventing excessive polymerization of the unsaturated hydrocarbons, the steps of; subjecting the motor fuel to successive separate applications of sulfuric acid of progressively stronger character; cooling the mixture of motor fuel and acid, toA absorb the heat of reaction after eachof such applications, to a temperature sufficiently low to permit a part -of the sulfur bodies to be selectively removed by said acid, and a part thereof'to be polymerized, and below the temperature at which the non-sulfur bearing unsaturated hydrocarbons readily polymerize; separating and removing the sludge from the motor fuel after each of said successive applications of sulfuric acid, and after the final separationy of sludge from said motor fuel, distill-ing the motor fuel from the polymerized bodies.

5. A sulfur removing process of treating motor fuels containing sulfur bearing bodies and nonsulfur bearing unsaturated hydrocarbons, in

which a part of the sulfur bearing bodies are.

removed by selective solvent action of sulfuric polymerized while excessive polymerization of the unsaturated hydrocarbons is prevented, which comprises contacting such motor fuel with sulfuric acid of v such strength and quantity as to have the capacity at low temperatures of selectively removing a part of the sulfur bodies and to polymerize a further part of said bodies and to effect a material rise of temperature of reaction unless restrained, conducting the treatment between the motor fuel and acid by contacting the motor fuel with acid in a series of steps, separating the resulting sludge from the motor 4fuel after each contact, applying the sludge from a late: acid treating step to the motor fuel at a point prior to said later acid treating step, applying the fresh acid as a last step in the process and applying the progressively stronger sludges to the progressivelyv more treated motor fuel, the acid treatments being performed, at av 'maximum temperature sufilciently low to permit a. part of the sulfur bodies 6 to be selectively removed by said acid and a. part thereof to be polymerzed, and below the temperature at which the non-sulfur bearing unsaturated hydrocarbons readily. polymerize, by cooling the mixture of motor fuel and acid during each application, separating the motor fuel from 

